AC power supplies can be used to supply AC power to electrical plasma processes such as plasma coating or plasma etching. AC power supplies for electrical plasma processes produce electrical powers whose frequency can be between a low-frequency range (for example, about 10 kHz) and a high-frequency range (for example, several or hundreds of MHz, up to several GHz, and in particular, values of 13 MHz, 27 MHz, 160 MHz, or 432 MHz). AC power supplies for electrical plasma processes generally include a generator having a defined real or complex internal resistance and an impedance matching circuit (matchbox) that matches the generally complex impedance of the plasma process or the plasma load to the internal resistance of the generator for improved or optimum power transmission. Since electrical plasma processes have the property of changing their impedance in a dynamic and non-predictable manner, and since undesirable local discharges (arcs) may further take place in the plasma and bring about an instantaneous change in impedance, the impedance matching circuit and optionally also the generator power are continuously adjusted or the flow of power from the generator to the plasma load can be completely interrupted.